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Aliment Pharmacol Ther. 2005 Nov 15;22(10):927-34.

Melatonin improves bowel symptoms in female patients with irritable bowel syndrome: a double-blind placebo-controlled study.

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Department of Pharmacology, National University of Singapore.



Melatonin is involved in the regulation of gastrointestinal motility and sensation.


To determine the potential therapeutic effects of melatonin in irritable bowel syndrome (IBS).


Seventeen female patients satisfying the Rome II criteria for IBS were randomized to receive either melatonin 3 mg nocte or identically appearing placebo 1 nocte for 8 weeks, followed by a 4-week washout period and placebo or melatonin in the reverse order for another 8 weeks. Three validated questionnaires - the GI symptom, the sleep questionnaires and the Hospital Anxiety and Depression Scale - were used to assess symptom severity and to compute the IBS, sleep and anxiety/depression scores, respectively.


Improvements in mean IBS scores were significantly greater after treatment with melatonin (3.9 +/- 2.6) than with placebo (1.3 +/- 4.0, P = 0.037). Percent response rate, defined as percentage of subjects achieving mild-to-excellent improvement in IBS symptoms, was also greater in the melatonin-treated arm (88% vs. 47%, P = 0.04). The changes in mean sleep, anxiety, and depression scores were similar with either melatonin or placebo treatment.


Melatonin is a promising therapeutic agent for IBS. Its therapeutic effect is independent of its effects on sleep, anxiety or depression.

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